DE2128065C2 - Phosphor layer for an electrical light source for generating white light and use of this phosphor layer - Google Patents

Description

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The invention relates to a Leuci fabric layer for a electric light source for the generation of white light, which contains three phosphor components that are used in a corresponding excitation in three different spectral ranges emit light, as well as the use -in formation of this phosphor layer.

Such a phosphor layer is already known from DE-OS 15 89 379, the known phosphor layer essentially provides a fluorescent lamp, which is for color photography and with which the spectrum 4> can be approximated by daylight. To this end, the lamp provides an essentially uninterrupted one Spectrum, as can be seen in Fig. 1 of the document, what by use a phosphor mixture is achieved, each> o include very broadband emitters. The combination of these phosphors results in a continuous Emission in the wavelength range from 375-685 nm. The emission spectrum does not contain any Gaps.

When it comes to the construction of fluorescent lamps, mar. On the one hand, achieve the highest possible light yield, but on the other hand, the best possible color rendering of illuminated objects should also be achieved. The fluorescent lamp of the ^h0 described type has good color rendering properties, their efficiency is but comparatively, (bad. This is because a relatively large amount of energy is radiated in spectral regions that are important for the lighting purpose of only secondary importance.

The object of the invention is to create a phosphor layer of the type mentioned, in which on the one hand, a light that corresponds as closely as possible to daylight is supplied, but a significantly higher efficiency than before.

This problem is solved in that the three spectral ranges are completely separated from each other and the phosphor components line or band-shaped in the spectral ranges 430-485 nm with a maximum Bandwidths of 40 nm, 515-570 nm with a maximum bandwidth of 80 nm and 588-635 nm intersect at a maximum bandwidth of 40 nm.

This separation of the spectral ranges and their very specific position is surprising Generates a white-appearing light, for the generation of which much less energy is required, than is the case with the prior art. Particularly It is surprising that in spite of the three relatively narrow spectral ranges that the with the invention A fluorescent lamp working with a fluorescent layer produces the generated light that is visible to the human eye appears and illuminated objects also show a largely natural color rendering.

The desired spectral distribution can be achieved particularly favorably by means of a phosphor layer, in which the phosphor component emitting in the range from 430-485 nm is replaced by a divalent Europium activated strontium chlorapatite, the phosphor component emitting in the range of 550-570 nm Calci- jmarsenid and those in the area of 588-630 nm emitting phosphor component through trivalent europium activated yttrium oxide is, the three components to each other in a weight ratio of the order of 17: 58: 25 standing.

The phosphor layer according to the invention can be in a fluorescent lamp, but also in an electroluminescent anoid.

The invention is explained in more detail below with reference to embodiments that are shown in Drawings are shown. It shows

Fig. 1 partially in section eiar side view of a fluorescent lamp coated with the fluorescent layer according to the invention:

Fig. 2 an x-. y-color diagram of the I.C.I. system (International Comission. Here publication C.I.E. No. 13 (E-I J.2.). 1965);

3 is a diagram showing the dependence of the color rendering index on the wavelength for each of the Illustrates three components that are mixed together to produce a particular white light are;

Fig. 4 is a graph showing the sensitivity of the human eye as a function of the light wavelength in nm:

F i g. 5 is a diagram showing the dependence of the relative yield on the wavelength for a inventive, representative mixture of light-emitting substances:

6 shows a diagram to illustrate the dependency the relative yield of the wavelength for the total emission of materials that form light generate a number of linear emissions;

F i g. 7 is a diagram showing the dependence of the relative yield on the wavelength for the Total emission of three different phosphors, two of which are so-called band emitters, during the third emits a group of lines, the main lines of the line emitter in the red area of the visible Spectrum lie;

F i g. 8 is a diagram showing the dependence of the relative yield on the wavelength for the Total emission of various phosphors, the blue component being a single band emitter and the middle one Component is a mixture of two band emitters, for which the sum of the outputs is shown as a dashed line is shown. and wherein the red component is a line-shaped emitter. its main lines in red Range of the visible spectrum;

9 is a perspective view of a die According to the invention, an electroluminescent arrangement using a phosphor layer;

F i g. 10 in partially broken away and in perspective View of a solid-state radiator using the arrangement according to the invention; and

11 shows a schematic view, partly in section an electrodeless discharge lamp that also makes use of the teachings of the invention.

Fig. 1 shows a generally designated 10, commercially available 40 W fluorescent lamp with a tubular Glass bulb 12, at the ends of which there would be retaining rings 14. Each bracket 14 has a Queüchfuß 16 with leads 18 on their inner ends wear coils 20 made of tungsten, for example. Inside the helix 20 is a conventional electron-emitting material! 22 provided.

Contact pins 24 extend from the ends of fluorescent lamp 10 via end caps 26 protrude. The inside of the bulb 12 is provided with a phosphor layer 28 made of a three-component mixture consists of different phosphors, as explained in detail below will. The flask is filled with argon or another inert ionizable gas at a pressure of For example, it is filled to 5.3 mbar to facilitate ignition, and also with a small amount of mercury 30. When such a lamp is operated, the gas discharge occurring between the electrodes is generated UV radiation with a wavelength of 253.7 nm and a limited amount of visible radiation.

The phosphor layer 28, which consists of finely ground material, has a three-component mixture made of different phosphors. A first component of the phosphor mixture has - at Excitation by the UV radiation generated by the discharge - an emission spectrum. that in is substantially centered in the green to yellow-green region of the visible spectrum. A second component of the mixture exhibits a line or very narrow-band emission. which are mainly in the orange to red area of the visible spectrum. The third component of the The mixture has a line emission or a very narrow-band emission. mainly in the purple-blue to the greenish-blue area of the visible spectrum. The proportions of the phosphor components to each other are chosen so that they are mixed with their emissions from the discharge generated visible emission, if such a visible emission occurs at all, white light with given ICI coordinates, and because of of the selected spectrum of the generated radiation is the color rendering of the objects illuminated by it: excellent.

F ^r ig. 2 shows the x, y color diagram of the ICI system in which the various colors are entered, which are represented by the letters which determine the colors of the current fluorescent lamps. The ICI color system is described in detail in the "Handbook of Colorimetry" by Arthur C. Hardy, Technology Press, Massachusetts Institute of Technology (1936). The color symbols entered in the ICI diagram have the following meanings;

symbol Lamp color A. Warm white B. Warm white de luxe C. White D. Cold white E. Cold white de luxe F. Reddish white G Bluish white H daylight

The ICl-LcuchfAcrt "C" is also shown and

corresponds to the color of natural daylight.

In general, any color that falls within the area enclosed by the dashed line is aem Eye as v-white «appears.

The first component has a green to yellow-green emission which is essentially in the wavelength range from 515 nm to 570 nm. This emission can be linear and / or band-shaped with a bandwidth of less than approximately 80 nm, measured with an emission intensity of 50% of the maximum measured emission intensity. The second j> component produces an orange-colored to red emission which lies essentially in the wavelength range from 588 nm to 630 μm, with essentially no infrared emission occurring. This emission can be linear and / or band-shaped, with a bandwidth of less than about 40 nm. The third component emits a purple-blue to greenish-blue emission, which is mainly in the wavelength range from 430 nm to 485 nm, with essentially no emission occurring in the UV range. This blue emission can be linear and / or band-shaped, with a bandwidth of less than approximately 40 nm, measured with an emission intensity of 50% <<> of the maximum measured emission intensity. Each of the line-shaped emissions can be a single line emission, the majority of which fall within the specified wavelength ranges. The band-shaped emissions can be a single bell-shaped band or a plurality of bands with an average band width corresponding to the specified values.

In Fig. 3 the display index is dependent plotted against the wavelength for all three emissions combined to generate white light. It fen is known that white light can easily pass through Combination of three wavelengths of about 450 nm. 500 nm and 575 nm can be generated, but it is not known that the color rendering for objects illuminated with such white light is extremely high would be bad. A piece of clothing illuminated with it would be completely different in daylight works. The same item of clothing would be illuminated with white light coming from the three different ones

Components purple-blue, yellowish-green and reddish-orange, with the wavelengths 450 nm, 535 nm and 610 nm, respectively, they would be obtained Colors of the illuminated objects are very good in the judgment of the normal observer. The curves of Fig.3 ϊ were obtained using three optimum emissions, namely 450 nm, 540 nm and 610 nm. Two of these three optimum emissions were kept at the aforementioned wavelengths, while the third emission was varied over a wide range to show the effect of color rendering The composite color of the resulting radiation mixture always remained the same in order to avoid the so-called. To generate "daylight white" light.

In FIG. 3 became the curve labeled "blue" obtained by the F.missions at 540 nm and 610 nm were held while the short wavelength radiations changed from 410 to about 500 ηm became. As shown, the color rendition measured according to the aforementioned CIF method has 2u beindex has a peak value. when the radiations go through the 450 nm value to a value of - 20 to decrease when the radiation has a wavelength of about 500 nm. The one labeled "green" Curve of FIG. 3 gives the results obtained by: 5 Retention of the 450 nm and 610 nm radiation and changes in the "mean" radiation from 500 nm to 575 nm were obtained. As can be seen, the radiations generated with a wavelength of 500 nm and 575 nm is a particularly poor color rendering of illuminated objects. The curve "red" in FIG. 3 was made by capturing the 450 nm and 540 nm radiations and changing the long-wave radiations received over the specified range

Radiations with a wavelength of less than 430 nm are practical in terms of achieving a good color rendering is only of marginal value, and these radiations are particularly weak with a view to producing a lighting for which the human eye to a great extent is sensitive. as shown with the eye sensitivity curve of Figure 4. Regarding the long wave Area of the visible spectrum in FIG. 3 are radiations with a wavelength of more than 630 nm very weak in terms of producing a good color rendering of illuminated objects, and how with the eye sensitivity curve of Figure 4 is shown even the eye is relatively insensitive to such radiation. Thus, the Presence of these radiations also increases the effectiveness of the generation of light by an artificial one Light source.

In practice it is desirable to keep the radiations in the range from 485 nm to 515 nm - see FIG. 3 - to a minimum, since they provide a color rendering index of less than 30. Similarly, it is desirable to keep the radiations in the range between 570 nm and 588 nm to a minimum, since they also only give a color rendering index of less than 30. Because of the high sensitivity of the ^fc0 human eye to yellow-green radiation is green yellow practical reasons sometimes desirable radiation to be used, the nm in the range of 565 to fall to 570 nm, said radiation delivering a relatively unfavorable for color reproduction.

To produce white light very effectively and objects with a compared to daylight

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40

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50 realistic color, the efficiency of the generated light - measured in lumens / watt - is limited to the proportion of electrical energy supplied to the light source, together with the efficiency of the conversion mechanism for generating visible light. If a significant proportion of the visible light generated has a wavelength of around 500 nm and 575 nm, the resulting efficiency for the light generated - measured in Lumen / Walt - can be relatively high, for example, but the color rendering of the illuminated objects can be completely unrealistic. However, if the light-emitting substances such as phosphors are selected so that they emit light having a wavelength corresponding to the wavelength at which the best color rendering index is obtained, as shown in FIG. 3 is shown. then both the efficiency - measured in lumens / watt - and the color rendering index of the resulting white irhtes can be excellent.

In Fig. 2 it is interesting to note that the Most of the yellow appearing radiations are kept to a minimum as far as possible in order to get one to obtain good color rendering of illuminated objects. In other words, the available energy is focused on other areas of the visible spectrum for the best possible efficiency To obtain light production (i.e. lumens / watt), together nv? »I a good color rendering of the illuminated ones Objects. This appears to be in contrast to the relatively high level of sensitivity of the human eyes are entitled to such yellow appearing radiation - see Fig. 4.

The following examples explain combinations of phosphor mixtures:

example 1

53% by weight of calcium arsenite _{(Zn 4} Ca _{3 PbISi 4} Oi ₆ : Mn) fluorescent, which occurs naturally as a mineral and which emits yellowish-green, is mixed with 12% by weight of erbium-activated yttrium phosphate, which emits blue, and 35 wt% europium activated lanthanum oxide emitting red mixed. The manganese-activated “middle” phosphor has a relatively broadband emission, as indicated generally with FIG. 5. The erbium-activated yttrium phosphate has a line-shaped emission spectrum in the blue region of the visible spectrum, as shown with the "blue" line in FIG. The europium-activated lanthanum oxide has a line-shaped emission, which is mainly in the red-orange to red range of the visible spectrum, as shown with the “red” line in FIG.

Example II

As a second example, the middle phosphor, whose emission spectrum is generally in the green to Centered in the yellow-green area of the visible spectrum is one or more line-emitting phosphors contain, an example of which is erbium-activated yttrium oxide, will contain 57% by weight of such Phosphor with 16% by weight of an erbium-activated yttrium phosphate and 27% by weight of a samarium-activated When mixed with lanthanum oxide, an emission spectrum composed of line emissions appears.

The middle component of the mixture can be from

other conventional phosphors whose emission spectrum is generally centered in the green to yellow-green region of the visible spectrum and has essentially no emission in the infrared or UV region. An example of such other phosphors is manganese-activated zinc silicate, which has a relatively narrow emission (bandwidth = 41 nm) with an apex at about 530 nm .

The proportions of the above mixtures are as follows chosen that a total of "white" light is emitted, with the procedure for setting the proportions such mixtures are well known. In connection with F i g. 2 can be any color for which the ICI coordinates are known with any other known color are mixed, the resulting ii The color of the mixture somewhere on the straight line between the two colors of the ICI diagram depending on the proportions of the components. If the ICI color coordinates of three individual phosphor components are known, it is therefore a simple matter. a mixture of a "white" -emitting phosphor to form, which in the dashed line in FIG. 2 delimited area falls.

Example 111

25th

Thulium-activated yttrium vanadate serves as the blue-emitting component. while terbium-activated yttrium vanadate serves as the green-emitting component and europium-activated yttrium vanadate as the red-emitting component. These phosphors are mixed in the correct ratio in order to produce white light of the desired color character. All of these rare earth-activated phosphors emit linearly, as shown in FIG. η Alternatively, the foregoing activating substances can be used together in the same base metal and emissions are substantially doubled, so that a single phosphor performs the function of three separate emission materials. The aforementioned activating substances can also be incorporated into phosphors of the sulfide type and these phosphors can then be excited by an electric field in accordance with generally known electroluminescence methods, so that they emit light. ⁴ "·

Example IV

A phosphor mixture is formed from the following components:

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1. by divalent europium-activated strontium chlorapatite, which is the blue component;

2. Calcium arsenite occurring as a natural mineral, which forms the middle, yellowish-green component; as

3. by trivalent europium-activated yttrium oxide, which forms the red-emitting component

These phosphors meet the requirements for the three separate phosphor components and, when combined in a weight ratio of 17: 58: 25, produce white light in a very effective manner in a conventional 40 W fluorescent lamp with very good color rendering. The respective emissions of the abovementioned phosphors are shown in FIG. 7, where ^{δ5 denotes} the blue-emitting phosphor with A, the yellowish green-emitting phosphor with B and the red-emitting phosphor with C.

Example V

In the phosphor mixture described as Example IV the mineral arsenite is replaced by the synthetic manganese-activated zinc germanate fluorescent. The weight ratio of chlorapatite to zinc germanate to yttrium oxide is 15: 42: 43.

Example VI

In the phosphor mixture mentioned as Example IV the mineral arsenite is activated by a mixture of arsenite "B" - see Fig. 8 - and by manganese Zinc germanate "D" - see Fig. 8 - replaced, with the resulting emission is shown with the dashed line in FIG. 8. The color rendering of a such phosphor mixture is excellent.

fig. 9 shows an electroluminescent arrangement 32 with electrodes 34 arranged at a distance from one another, at least one of which is transparent and which include a phosphor 36 between them, which forms a layer 38 in translucent dielectric material is embedded. Both electrodes are preferably covered by protective layers 40, 42. In this arrangement the phosphor has a mixture of copper-activated zinc sulfide. that emits blue, as well as copper and manganese activated zinc sulfide, which emits yellow-green, and copper activated zinc selenide or copper-activated mercury zinc sulfide, which emits red.

10 shows a further embodiment of a lighting arrangement 44 with a combination of emitters of the transition type and electroluminescence, the individual emission components being mixed with one another by a light-scattering layer. Electrodes 46 and 48, which are arranged at a distance from one another and to which a direct voltage potential can be applied, enclose a series of junctions 50 between them. For example, the junctions 50Ga (P ₁ Sb) - a red-emitting junction - and in this exemplary embodiment the blue and yellow-green emitting components of the electroluminescent portion of the arrangement can then be formed by copper-activated zinc sulfide, as was explained above . Instead, the transition emitters can contain a mixture of yellow-green emitting junctions such as silicon carbide and the red-emitting junctions such as the Ga (P, Sb) mentioned. In this exemplary embodiment, only the blue-emitting component of the conventional electroluminescent part of the arrangement needs to be provided. The electroluminescent part of the arrangement can be excited by an alternating or equal voltage potential fed to the electrodes 48 and 52. The light-emitting portion of the arrangement is surrounded by a translucent cup-shaped body 54 which carries a coating 56 made of light-scattering material such as magnesium, which diffusely mixes the emitted radiation with one another

Another embodiment of an "electrodeless" discharge arrangement 58 is shown in FIG Assembly 48 includes a glass bulb 60 that is under low pressure to maintain gas suitable for gas discharge such as argon and small amounts of vaporizable rare earth metals 62 or rare earth metal compounds such as thulium, terbium and europium or thulium iodide, terbium iodide and europium iodide is filled, the assembly 58 is connected to an RF source by means of a surrounding it

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connectable winding 64 excited, so white light with a spectral energy distribution is similar F i g. 6 generated. In this case the tlftulium produces or Thulium iodide the blue emission, the terbium or terbium iodide the green emission and dai; Europium or europium iodide the red emission. Instead, thulium can be replaced by bismuth, terbium by erbium and / or europium can be replaced by strontium.

According to a further modified embodiment The discharge arrangement 58 can be provided with a fluorescent layer 65 on its inside be in order to receive the additional radiation, and phosphor mixtures can also be used as with the Examples described above are used.

For this purpose 4 sheets of drawings

Claims (3)

Patent claims: 1. Phosphor layer for an electric light source to generate white light, the three It contains three different fluorescent components when excited Spectral ranges emit light, thereby characterized in that the three spectral ranges are completely separated from each other and the Phosphor components in the form of a line or band in the spectral ranges from 430 to 485 nm at a maximum bandwidth of 40 nm, 515 to 570 nm with a maximum bandwidth of 80 nm and 588 to Emit 630 nm with a maximum bandwidth of 40 nm. 2. phosphor layer according to claim 1, characterized in that the range from 430 nm to 485 nm emitting fluorescent component through divalent europium activated slrontium chlorapatite. d'e in the range from 515 to 570 nm emitting phosphor component calcium arsenide and the phosphor component emitting in the range from 588 to 630 nm is ytrium oxide activated by trivalent europium, the three components to each other in a weight ratio on the order of 17: 58: 25 standing. 3. Use of the phosphor layer according to claim 1 or 2 in a fluorescent lamp or an electroluminescent arrangement 30th